Power combiners and directional couplers are passive microwave devices that can be used to combine electrical signals in the radio frequency (RF) range (i.e. frequencies in the range of about 3-300 MHz) or microwave frequency range (i.e. frequencies above about 300 MHz). Power combiners can be used in amplifier modules that comprise multiple unit amplifiers. For instance, an amplifier module may include four unit amplifiers and the output of each unit amplifier can be combined together using a 4:1 combiner to produce the required total output power of the amplifier module.
With the advancement of transistor technology in the RF and microwave frequency ranges, it is now possible to generate higher RF power levels using semiconductor devices. Accordingly, a need exists for compact stripline/coaxial combiners which can reliably combine RF and microwave signals having power levels in the range of about 10 kW and above.
However, current combiner technology that uses air suspended stripline or classic stripline/microstrip technology has insufficient thermal dissipation for the power levels which the combiner will be subjected to. In addition, the coupling performance of the combiners can be sensitive to thermal expansion and very sensitive to misalignment. Furthermore, waveguide technology is too large to be used in combiners for certain applications.